Organobismuth(III) dihalides with T-shaped geometry stabilized by intramolecular N→Bi interactions and related diorganobismuth(III) halides

Organobismuth(III) compounds containing (N,C,N)-pincer ligands were prepared and characterized both in solution and in the solid state. Compound RBiCl2 1 [R = 2,6-(Me2NCH2)(2)C6H3] was obtained from RLi and BiCl3 (1:1 molar ratio). RBiBr2 2 and RBiI2 3 were obtained by halogen-exchange reactions from 1. Reaction of 1 with MeMgI afforded RBi(Me)I 4. Compound R2BiCl 5, obtained from RLi and BiCl3, is rearranged in solution to 1 and R3Bi. The molecular structures of compounds 1-5 were established by single-crystal X-ray diffraction. All dihalides RBiX2 show a T-shaped CBiX2 core. They are the first stable compounds corresponding to the edge inversion "transition state" at the bismuth center, stabilized by two strong intramolecular N -> Bi interactions in trans positions to each other, which contribute to an overall distorted square pyramidal (N,C,N)BiX2 coordination geometry. The electronic structure of [2,6-(Me2NCH2)(2)C6H3]BiCl2 (1) was analyzed by density functional theory (DFT) calculations, which provide evidence that the stabilization of the square pyramidal geometry of bismuth is electronic rather than steric in nature.